Re: [PATCH] stable-fixup: hotplug: fix unused function warning

[Michal Hocko]

On Mon 09-01-17 11:47:50, Arnd Bergmann wrote:
> The backport of upstream commit 777c6e0daebb ("hotplug: Make
> register and unregister notifier API symmetric") to linux-4.4.y
> introduced a harmless warning in 'allnoconfig' builds as spotted by
> kernelci.org:
> 
> kernel/cpu.c:226:13: warning: 'cpu_notify_nofail' defined but not used [-Wunused-function]

Is this warning really worth bothering? Does any stable rely on warning
free builds?

> So far, this is the only stable tree that is affected, as linux-4.6 and
> higher contain commit 984581728eb4 ("cpu/hotplug: Split out cpu down functions")
> that makes the function used in all configurations, while older longterm
> releases so far don't seem to have a backport of 777c6e0daebb.
> 
> The fix for the warning is trivial: move the unused function back
> into the #ifdef section where it was before.

this looks good to me.

> Link: https://kernelci.org/build/id/586fcacb59b514049ef6c3aa/logs/
> Fixes: 1c0f4e0ebb79 ("hotplug: Make register and unregister notifier API symmetric") in v4.4.y
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>  kernel/cpu.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index cd6d1258554e..40d20bf5de28 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -223,10 +223,6 @@ static int cpu_notify(unsigned long val, void *v)
>  	return __cpu_notify(val, v, -1, NULL);
>  }
>  
> -static void cpu_notify_nofail(unsigned long val, void *v)
> -{
> -	BUG_ON(cpu_notify(val, v));
> -}
>  EXPORT_SYMBOL(register_cpu_notifier);
>  EXPORT_SYMBOL(__register_cpu_notifier);
>  
> @@ -245,6 +241,11 @@ void __unregister_cpu_notifier(struct notifier_block *nb)
>  EXPORT_SYMBOL(__unregister_cpu_notifier);
>  
>  #ifdef CONFIG_HOTPLUG_CPU
> +static void cpu_notify_nofail(unsigned long val, void *v)
> +{
> +	BUG_ON(cpu_notify(val, v));
> +}
> +
>  /**
>   * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
>   * @cpu: a CPU id
> -- 
> 2.9.0
> 

-- 
Michal Hocko
SUSE Labs